The following long-term study will be completed: ten groups of mice (12 per group) were treated with dimethylbenzanthracene, followed by promoter (TPA) once weekly, and retinoic acid (RA) (or control vehicle without retinoic acid), to determine whether retinoic acid applied during the promotion stage, or the papilloma stage, or the papilloma-to-carcinoma stage, or the carcinoma stage, can affect tumor incidence and glycoprotein synthesis. The skin or tumor samples at the respective stages are being incubated with labeled glycoprotein precursors or examined histologically. RA-treatment appears to be correlated with suppression of a tumor sialomucin and stimulation of a high-glucosamine, mannose-containing glycoprotein, at the same time as lowering tumor incidence. The sialomucin characteristic of the skin tumor, and the stimulated high-glucosamine, mannose-containing glycoprotein following RA application, will be isolated and characterized by lectin binding, by sugar analysis, by digestion to glycopeptides, by affinity chromatography (depending on lectin-binding properties), by iodine labeling, and attempts will be made to prepare antibodies to the glycoproteins, and to locate them to the cell surface, as is suspected. The induction of the enzyme ornithine decarboxylase (ODC) during tumor promotion, and its suppression by RA, will be explored, to test the hypothesis that the glycoprotein stimulated by RA is the inhibitory agent of ODC induction.